Symptoms of adult onset dermatomyositis
What are the characteristic clinical features of adult onset dermatomyositis
• Rash is the first clinical manifestation (see Question 4). No mechanic’s hands.
• Muscle disease follows or coexistent with rash with 70% having elevated muscle enzymes and 20% to 30% having normal CPK (amyotrophic DM), although aldolase and/or muscle MRI may be abnormal (hypomyopathic DM).
• MSAs found in 50% to 70% and identify clinical subsets.
• Muscle pathology: perimysial/perivascular inflammation with (50%) or without (50%) perifasicular atrophy. Inflammatory infiltrate primarily B cells, CD4+ T cells, and plasmacytoid dendritic cells that produce interferon-α, which contributes to atrophy. Complement C5b-9 membranolytic attack complex found on endothelial cells associated with reduction of endomysial capillaries and microinfarcts.
• Usually good prognosis (5-year survival [5YS] 92%). If associated with cancer, 5YS is 62%.
